Method and device for determining aspect angle progression
View Patent ↗A method and a device are provided for specifying, in the context of the image generation of ISAR processing, the determination of the aspect angle course subject to which the radar illuminates the vehicle during the exposure and subject to which the vehicle echoes are reflected back to the radar. Using the distance between the radar sensor and the vehicle as well as the change in distance, both of which are determined from the radar data, the position and the velocity of the vehicle are determined at any time during the exposure through linkage with available road information. The aspect angle is then determined from the positions of the sensor and of the vehicle as well as from the direction of movement of the vehicle. The required road information can be acquired from digital maps or images (e.g. aerial photographs, SAR-images).
1. A method for determining the progression of an aspect angle, the method comprising:
illuminating, by an aircraft- or satellite-borne Inverse Synthetic Aperture RADAR (ISAR), a vehicle traveling on a road;
receiving, by a radar sensor, echoes reflected back from the vehicle to the radar, wherein the radar signals themselves are used for determining the aspect angle;
determining, by an ISAR processor, distances and changes in distance between the radar sensor and the vehicle and between the radar sensor and a thoroughfare;
determining, by the ISAR processor, positions of the vehicle for every point in time during an exposure of the vehicle by the radar using the determined distance, change in distance, and road information obtained from a database of thoroughfares in an area illuminated by the radar;
determining, by the ISAR processor, velocity vectors of the vehicle at the determined positions of the vehicle using geometric conversions;
combining, by the ISAR processor using a mathematical process, the determined positions of the vehicle, the determined velocity vectors of the vehicle and a movement model of the vehicle, wherein contributions from the movement model and the determined positions of the vehicle and determined velocity vectors of the vehicle are weighted according to their accuracy;
determining, by the ISAR processor using a geometric calculation, an aspect angle of the illumination of the vehicle for each moment of the exposure from a viewing direction between radar sensor and vehicle, wherein the viewing direction is a direction of a connecting line from the radar sensor to the vehicle that results from positions of the sensor and the vehicle and the direction of the velocity vector of the vehicle whose direction coincides with the vehicle longitudinal axis.
2. A non-transitory storage medium that includes a computer program, which when executed by a processor causes the processor to:
illuminate, by an aircraft- or satellite-borne Inverse Synthetic Aperture RADAR (ISAR), a vehicle traveling on a road;
receive, by a radar sensor, echoes reflected back from the vehicle to the radar, wherein the radar signals themselves are used for determining the aspect angle;
determine distances and changes in distance between the radar sensor and the vehicle and between the radar sensor and a thoroughfare;
determine positions of the vehicle for every point in time during an exposure of the vehicle by the radar using the determined distance, change in distance, and road information obtained from a database of thoroughfares in an area illuminated by the radar;
determine velocity vectors of the vehicle at the determined positions of the vehicle using geometric conversions;
combine, using a mathematical process, the determined positions of the vehicle, the determined velocity vectors of the vehicle and a movement model of the vehicle, wherein contributions from the movement model and the determined positions of the vehicle and determined velocity vectors of the vehicle are weighted according to their accuracy;
determine, using a geometric calculation, an aspect angle of the illumination of the vehicle for each moment of the exposure from a viewing direction between radar sensor and vehicle, wherein the viewing direction is a direction of a connecting line from the radar sensor to the vehicle that results from positions of the sensor and the vehicle and the direction of the velocity vector of the vehicle whose direction coincides with the vehicle longitudinal axis.